java - 尝试保存在内部位图图片

Question

该应用程序是当成员单击 btn 相机打开并拍照并在 ImageView 中看到它时。当他关闭应用程序时，图片需要保存在内部存储中。 问题是当我点击 btn 并在拍照后点击 V 时，应用程序崩溃了/

package com.e.test;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.provider.MediaStore;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

全局变量:

    final int CAMERA_REQUEST = 1;
    ImageView imageview;
    Bitmap bitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

这是加载图像:

        try {
            FileInputStream fis = openFileInput("pictures");
            bitmap = BitmapFactory.decodeStream(fis);
            imageview.setImageBitmap(bitmap);
            fis.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        Button btn = findViewById(R.id.btn);
        imageview = findViewById(R.id.image_result);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                startActivityForResult(intent,CAMERA_REQUEST);

            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == CAMERA_REQUEST && resultCode == RESULT_OK)
        {
            bitmap = (Bitmap)data.getExtras().get("data");
            imageview.setImageBitmap(bitmap);
        }
    }

这是保存:

    @Override
    protected void onPause() {
        super.onPause();
        try {
            FileOutputStream fos = openFileOutput("pictures",MODE_PRIVATE);
            bitmap.compress(Bitmap.CompressFormat.JPEG,50,fos);
            fos.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

Answer 1

NullPointerException 发生是因为您的bitmap 实例为空。不确定您如何使用此代码，但您可以添加空检查以确保 bitmap 在您对其执行操作(例如压缩)时不为空。那么你的应用程序就不会崩溃。像这样:

@Override
protected void onPause() {
    super.onPause();
    try {
        if(bitmap != null){
            FileOutputStream fos = openFileOutput("pictures",MODE_PRIVATE);
            bitmap.compress(Bitmap.CompressFormat.JPEG,50,fos);
            fos.close();
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}